People who loose their sense of smell (current estimates place this figure three million or more) may experience a shift in the quality of their life -- some even recognize the compromise in health and safety resulting from anosmia (e.g., inability to smell spoiled food or natural gas). Depression or shifts in weight may be evident. Unfortunately, olfaction is one of the least understood sensory systems and little can be done to restore the sense of smell in most people. Knowledge about how genes and the environment interact to mediate olfaction can contribute to a better understanding of odor perception. Studies of specific anosmias (selective deficits in otherwise normal people) can provide some of this information. Specific anosmia to androstenone has a genetic origin. This phenotype, however, is dynamic: It is influenced by developmental and experimental factors. Most young children can smell androstenone. At about the time of puberty, many individuals become androstenone-anosmic. The ability to smell androstenone, however, can be induced in half of androstenone-anosmics by selective exposures to the compound. Using psychophysical, cytogenetic, histological and classical genetic methods further explorations of the mechanisms underlying specific anosmia to androstenone will be undertaken and the peculiar shift from anosmia that can be induced by experience will be studied in depth. Additional work will determine whether the observed changes in the perception of androstenone are unique to androstenone or generalize to other odors. Animal models would provide ideal tools for understanding olfactory processing at the biochemical and physiological levels. To these ends, a model of androstenone anosmia is being developed and tested to determine its adequacy.